This invention relates to a mobile radio unit formed as a radio selective call receiver, a portable phone and the like in the time division multiplexing communication system and, more particularly, to a mobile radio unit provided with an automatic gain control circuit in its receiving section.
A conventional mobile radio unit has been provided with an automatic gain control circuit so that the received signal level is controlled within a predetermined level upon demodulating and decoding the received signal. The mobile radio unit is often used in the condition where electric field level is likely to change, leading to fluctuation in the reception level. In order to cope with the above problem, the automatic gain control circuit has been constructed to detect a received signal strength (an electric field strength of the received signal) and adjust amplification degree based on the detected received signal strength so as to keep an output level to a predetermined level.
Japanese Patent Application Laid-Open NO. 170165 (1986) has disclosed an invention improving follow-up ability to suitably receive burst signals.